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Background/Objectives: The World Health Organization has selected enterococci as one of the priority multidrug-resistant microorganisms for the development of new antibacterial drugs. Bacteriophages are promising antibacterial agents, but the biology of bacteriophages requires deeper understanding. Methods: The vB_EfS_SE phage which is capable of infecting four species of the genus Enterococci was isolated from sewage plant. The complete genome of the vB_EfS_SE phage was sequenced using illumina technology. The endolysin gene was cloned into pBAD18 expression vector. Two chimeric endolysins were engineered using the vB_EfS_SE carbohydrate-binding domain (CBD) and replacing its enzymatically active domain (EAD). Results: The bacteriophage exhibits promising lytic properties and persists at temperatures of 40 °C and below, and under pH conditions ranging from 5 to 11. The genome sequence is 57,904 bp in length. The vB_EfS_SE endolysin PlySE and chimeric endolysins PlyIME-SE and PlySheep-SE were found to have the same range of specificity, but different thermostability properties and a different pH range for enzyme activity. Conclusions: Taking together the results obtained in this work and other published studies, we can highly appreciate the potential of Saphexavirus phages and their endolysins as novel antibacterial compounds.

A novel conductive composite based on PEDOT:PSS, BSA, and Nafion for effective immobilization of acetic acid bacteria on graphite electrodes as part of biosensors and microbial fuel cells has been proposed. It is shown that individual components in the composite do not have a significant negative effect on the catalytic activity of microorganisms during prolonged contact. The values of heterogeneous electron transport constants in the presence of two types of water-soluble mediators were calculated. The use of the composite as part of a microbial biosensor resulted in an electrode operating for more than 140 days. Additional modification of carbon electrodes with nanomaterial allowed to increase the sensitivity to glucose from 1.48 to 2.81 μA × mM−1 × cm−2 without affecting the affinity of bacterial enzyme complexes to the substrate. Cells in the presented composite, as part of a microbial fuel cell based on electrodes from thermally expanded graphite, retained the ability to generate electricity for more than 120 days using glucose solution as well as vegetable extract solutions as carbon sources. The obtained data expand the understanding of the composition of possible matrices for the immobilization of Gluconobacter bacteria and may be useful in the development of biosensors and biofuel cells.

Biosensors based on an oxygen electrode, a mediator electrode, and a mediator microbial biofuel cell (MFC) using the bacteria Gluconobacter oxydans B-1280 were formed and tested to determine the integral toxicity. G. oxydans bacteria exhibited high sensitivity to the toxic effects of phenol, 2,4-dinitrophenol, salicylic and trichloroacetic acid, and a number of heavy metal ions. The system “G. oxydans bacteria–ferrocene–graphite-paste electrode” was superior in sensitivity to biosensors formed using an oxygen electrode and MFC, in particular regarding heavy metal ions (EC50 of Cr3+, Mn2+, and Cd2+ was 0.8 mg/dm3, 0.3 mg/dm3 and 1.6 mg/dm3, respectively). It was determined that the period of stable functioning of electrochemical systems during measurements was reduced by half (from 30 to 15 days) due to changes in the enzyme system of microbial cells when exposed to toxicants. Samples of the products made from polymeric materials were analyzed using developed biosensor systems and standard biotesting methods based on inhibiting the growth of duckweed Lemna minor, reducing the motility of bull sperm, and quenching the luminescence of the commercial test system “Ecolum”. The developed bioelectrocatalytic systems were comparable in sensitivity to commercial biosensors, which made it possible to correlate the results and identify, by all methods, a highly toxic sample containing diphenylmethane-4,4′-diisocyanate according to GC-MS data.

In the last decade, there has been continuous competition between two methods for detecting the concentration of dissolved oxygen: amerometric (Clark electrode) and optical (quenching of the phosphorescence of the porphyrin metal complex). Each of them has obvious advantages and disadvantages. This competition is especially acute in the development of biosensors, however, an unbiased comparison is extremely difficult to achieve, since only a single detection method is used in each particular study. In this work, a microfluidic system with synchronous detection of the oxygen concentration by two methods was created for the purpose of direct comparison. The receptor element is represented by Saccharomyces cerevisiae yeast cells adsorbed on a composite material, previously developed by our scientific group. To our knowledge, this is the first work of this kind in which the comparison of the oxygen detection methods is carried out directly.

One of the main indices of the quality of water is the biochemical oxygen demand (BOD). A little over 40 years have passed since the practical application of the first microbial sensor for the determination of BOD, presented by the Japanese professor Isao Karube. This time span has brought new knowledge to and practical developments in the use of a wide range of microbial cells based on BOD biosensors. At present, this field of biotechnology is becoming an independent discipline. The traditional BOD analysis (BOD5) has not changed over many years; it takes no less than 5 days to carry out. Microbial biosensors can be used as an alternative technique for assessing the BOD attract attention because they can reduce hundredfold the time required to measure it. The review examines the experience of the creation and practical application of BOD biosensors accumulated by the international community. Special attention is paid to the use of multiple cell immobilization methods, signal registration techniques, mediators and cell consortia contained in the bioreceptor. We consider the use of nanomaterials in the modification of analytical devices developed for BOD evaluation and discuss the prospects of developing new practically important biosensor models.

Biomembranes based on an organosilica sol–gel matrix were used to immobilize bacteria Paracoccus yeei VKM B-3302 as part of a biochemical oxygen demand (BOD) biosensor. Diethoxydimethylsilane (DEDMS) and tetraethoxysilane (TEOS) were used as precursors to create the matrix in a 1:1 volume ratio. The use of scanning electron microscopy (SEM) and the low-temperature nitrogen adsorption method (BET) showed that the sol–gel matrix forms a capsule around microorganisms that does not prevent the exchange of substrates and waste products of bacteria to the cells. The use of DEDMS as part of the matrix made it possible to increase the sensitivity coefficient of the biosensor for determining BOD by two orders of magnitude compared to a biosensor based on methyltriethoxysilane (MTES). Additionally, the long-term stability of the bioreceptor increased to 68 days. The use of such a matrix neutralized the effect of heavy metal ions on the microorganisms’ catalytic activity in the biosensor. The developed biosensor was used to analyze water samples from water sources in the Tula region (Russia).

Microorganism-cell-based biohybrid materials have attracted considerable attention over the last several decades. They are applied in a broad spectrum of areas, such as nanotechnologies, environmental biotechnology, biomedicine, synthetic chemistry, and bioelectronics. Sol-gel technology allows us to obtain a wide range of high-purity materials from nanopowders to thin-film coatings with high efficiency and low cost, which makes it one of the preferred techniques for creating organic-inorganic matrices for biocomponent immobilization. This review focuses on the synthesis and application of hybrid sol-gel materials obtained by encapsulation of microorganism cells in an inorganic matrix based on silicon, aluminum, and transition metals. The type of immobilized cells, precursors used, types of nanomaterials obtained, and their practical applications were analyzed in detail. In addition, techniques for increasing the microorganism effective time of functioning and the possibility of using sol-gel hybrid materials in catalysis are discussed.